Fixes https://jira.springsource.org/browse/ROO-1213 - Hide Property from public API, and https://jira.springsource.org/browse/ROO-1274 - Remove PropertyReference and Value.

Properties are now computed from the *Proxy classes and emitted into the generated *ProxyImpl classes.  Server side code will infer what the properties should be by reflecting over the *Proxy classes looking for bean-like property methods.  PropertyReference depends on Property so it was also removed from the public API.

Review at http://gwt-code-reviews.appspot.com/842803

Review by: amitmanjhi@google.com

git-svn-id: https://google-web-toolkit.googlecode.com/svn/trunk@8780 8db76d5a-ed1c-0410-87a9-c151d255dfc7